#48 Moon Data Problems

Dave Hahne

The data for moon rise and set times appear to be in error when
compared to US Naval Observatory ephemeris. Also, for a date of
October 2, 2004 when changing between 4:10PM and 4:11PM the
rise time for the moon changes from 8:30PM to 9:03PM. Lat/long
inputs are 37d9m N and 76d23m W and I am manually adjusting
for daylight savings time. I have version 2.5.1 and version 4.1 of
the Palm OS.


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    Please note the "-" and "+" sign after the rise/set time, which
    tell you that this time is for previous resp. next day. In astroinfo
    the data is displayed so that rise time < set time, which means
    that often one of the times has to fall on the next or previous
    day. It chooses the rise/set time so that the transit time is
    nearest to the current time, so it may depend on the current

  • Dave Hahne
    Dave Hahne

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    The errors in rise/set time are typically less than 1 hour and are not
    issues with the day. I'm not sure I understand your comment about
    AstroInfo choosing the rise/set time so that the transit time is nearest
    the current time. Shouldn't the transit time for a given date and location
    be constant and not a function of the current time?

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    I tried it with several different days for your location and
    checked with the times given me ba US Naval Observatory at
    The rise/set times in astroinfo were always at most 1 minute
    away from the times calculated by the above web page.

    Regarding the transit times: There is one transit before the
    current time and one transit after. Astroinfo chooses the one
    that is nearer. So if moon transit is shortly after midnight and it
    is 11 pm, it chooses the transit that happens in few hours
    instead of the transit that happened more than 20 hours ago
    but on the same day.
    So for 4:10 PM it shows the previous transit
    8:30PM (-) to 11:10AM
    and at 4:11PM it show the next transit
    9:03PM to 12:12PM(+)

  • Dave Hahne
    Dave Hahne

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    Looked at the data/display more closely. I now understand what you
    were saying about the dates. Thanks for your patience with my

  • Michael Heinz
    Michael Heinz

    • status: open-invalid --> closed-invalid